I'm not familiar with node.js, but don't most JavaScript libraries already run in both the browser (including Electron) and node.js?
Is it a matter of significantly different system APIs and standard libraries, and this offers a bridge for applications expecting to run in Node, providing that environment in the JavaScript context of a browser? (Or does it actually run Node in WASM?)
But if you do, then this attempts to solve that problem.
If you're asking what's the use case for running nodejs in the browser? I say use your imagination.